Two reactions:
1. I think we should stay away from 'stream' here.
If Racket had grown out of the Unix tradition, I'd
be fine with it. But we partially grew out the
functional community, and they use 'stream' for
a narrower concept.
2. My hunch is that immutable 'things' are what we
want. So unless someone has a good example of why
a vector should be a 'thing' as opposed should be
converted to a 'thing', speak up now or be quiet
forever.
-- Matthias
p.s. And I agree with Eli and you that generator
should remain for what is now know as a Python
concept but which appeared in Icon and Snobol
decades before -- under the same name.